低温高SV动静结合型机械密封液气相变机理及其非稳态效应研究

动静结合型机械密封是清洁低温燃料液体火箭发动机高速涡轮泵关键部件，其典型服役条件为低温和热力效应下的高应力×速度值（高SV值）。结合前期试验发现的此类密封极易在起动及高速阶段出现严重摩擦与液气相变的现象，拟开展低温高SV动静结合型机械密封相变机理及其非稳态效应研究。首先，发展考虑热力效应、边界润滑、固体变形以及补偿力作用下的热-流-固-力多场耦合摩擦模型，以此阐明密封在接触状态下的热-力-摩擦学耦合机理及产生相变的沸腾及闪蒸机制。其次，构建考虑相变和接触的机械密封起动脱开模型和高速密封-轴承-转子系统的动力稳定性模型，以此解释机械密封的失稳起飞机制和热相变非稳态效应行为。最后，开展系列单项及模拟试验，完成对耦合摩擦模型、液气相变模型、多工况密封静动性能求解模型的验证。研究结果对于获知复杂工况机械密封服役性能演变规律和保证机组安全运行具有重要的科学意义，对提高国防核心竞争力具有重要工程价值。

The hydrodynamic mechanical seal is the key component of the high-speed turbopump in the clean cryogenic fuel liquid rocket engine. The typical working characteristics of the seal are the high Stress multiply Velocity value (high SV value) from the cryogenic condition and thermal-mechanical effect. Combined with the preliminary experimental results and the discovered severe friction and liquid-gas phase change phenomenon of the seal during the transient start-up and high-speed running stage, the study on liquid-gas phase change mechanism and its unsteady state effect for the cryogenic and high SV hydrodynamic mechanical seal system is proposed. Firstly, considering the thermal-mechanical effect, fluid boundary lubrication, seal rings' deformation and elastic compensation force from the supported springs, a three-dimensional thermo-elastic-hydrodynamic-mechanical multi-field coupling contact-friction model is developed, which will be used to clarify the thermo-mechanical-tribological coupling mechanism of the seal in the contact state and the boiling and flashing mechanisms that cause liquid-gas phase changes. Secondly, with considering the phase change and contact conditions, a dynamic take-off model of contact mechanical seal and a dynamic stability model of the seal-bearing-rotor system under high-speed condition are proposed. Based on both models, the instability take-off mechanism of mechanical seal and the non-steady state effect of liquid-gas phase change behavior will be explained. Finally, a series of special tests and simulation running experiments will be carried out to verify the multi-field coupled contact-friction model, the liquid-gas phase change model, the mult-condition static and dynamic performance model for full service life. The research results have the important scientific significance for understanding the evolution mechanism on the service performance of the hydrodynamic mechanical seal and ensuring the safe and reliable work of the high-speed turbopump under the complex and multi-varied running conditions, which have important engineering value for improving the core competitiveness of national defense.